[6] During his professional career which spanned nearly 20 years, Walton refereed a number of notable matches, including the 2003 final of the Football League Trophy and the FA Community Shield in 2008.

In 1996, he was an assistant referee for the FA Cup final at Wembley Stadium, when Manchester United defeated Liverpool with a late Eric Cantona goal.

In 2003, he was added to the Select Group of referees and took charge of the Football League Trophy final between Bristol City and Carlisle United on 6 April, with the Robins triumphing 2–0.

He then took up a new role as the general manager of the Professional Referee Organization (PRO) for the Football Leagues in the United States and Canada, from 2 April 2012.

"[16] Walton currently works as a referee analyst for BT Sport's coverage of the UEFA Champions League, discussing key decisions and explaining the usage of VAR, both in-game and post-match.